The invention relates to a novel process representing a real contribution to the art of applying dyestuffs and/or chemicals or finishing agents to textiles, fibrous products, sheet materials, papers or fleeces.
Dyestuffs or chemicals are generally applied to textiles by letting the fabrics undergo a saturation treatment through immersion or padding in a liquid bath, after which the excess liquor is pressed out and the fabrics dried. If the cloth has been impregnated with resins, the latter are cured, usually during the drying or also after the drying. However, in the padding process it is a disadvantage that the cloth must be completely dipped into the padding liquid, the take-off speed being dependent upon the drying process. In addition, large quantities of water are required for drying the cloth, resulting in high cost.
Attempts have been made to overcome the disadvantages of the padding method for applying finishing materials to textiles by spraying the chemicals or dyestuffs dispersed in liquids. To spray textiles with chemicals or liquid dyestuffs, it is common practice to apply these substances via spray heads or guns that utilize compressed air as a means for carrying the dyestuffs or chemicals. Thus, German Pat. No. 950 187 recites such a process and a device for imparting colorfastness to colored textiles and the like, whereby the liquid is atomized as a mist with the aid of a jet of air serving at the same time as a means for delivering the mist. Likewise, the printed publication of German Unexamined Patent Specification No. 241 6 221 recites a spray method for applying finishing agents, wherein a concentration of the finishing is atomized on the material as a fine watery spray produced in a device employing compressed air.
These well-known spray methods obviate the drawbacks of the padding method, but they themselves have serious disadvantages. With the known spray technology using compressed air as carrier, it is impossible to coat textiles uniformly with dyestuffs and/or chemicals or finishing agents. Turbulences arise at the interface between two different atomizing cones, resulting in uneven coating. Likewise, turbulences can be formed within an atomizing cone directly on the outlet edge of the nozzle, which may lead to uneven distribution of the sprayed material within an atomizing cone.
Therefore, the major purpose of the invention is to provide a process of the type mentioned at the outset, by which textiles, fibrous products, sheet materials, papers or fleeces can be uniformly coated with dyestuffs and/or chemicals or finishing agents.
The above object is solved according to the invention by applying the dyestuffs and/or chemicals in the electrostatic field, that is, by attracting the dyestuffs and/or chemicals to the object to be painted by an electrostatic potential.
According to a preferred embodiment of the invention, the process is carried out in the indirect electrostatic field, that is, the process makes use of indirect electrostatic potential.
Another preferred embodiment of the process of the invention employs the hydraulic spray method known as airless spraying, wherein the liquid is atomized under very high pressure without air as carrier medium and only the minimum quantity of the liquid necessary for solving the dyestuffs or chemicals is atomized and applied to the textiles.
A further preferred embodiment of the invention uses equipment with two-fuel spray nozzles.
A great number of techniques representing a real contribution to the art can be achieved with the process provided by the invention.
The process according to the invention permits higher production rates in all fields of application. It is distinguished by an enormously reduced water consumption, far below the proportions employed in the padding technique. Moreover, the cost of energy is significantly lowered, since less moisture has to be evaporated in the drying zone, which results in a lower cost per meter produced.
The process according to the invention can be employed in all semi- or fully continuous methods independently of the nature of the materials which, for example, may consist of spun yarns, flocks, non-woven fabrics, warp yarns, woven fabrics, or knitted goods, as well as fleeces.
A special advantage of the process of the invention lies in the fact that, unlike the padding method, there is no need for squeeze rollers and, thus, processing with high liquor concentrations is possible without the risk of liquor breakdown, such as occurs in the processes heretofore employed.
Another important advantage of the method of the invention lies in the fact that dyestuffs and/or chemicals or finishing agents, as the case may be, can be applied to materials that are inherently very sensitive to pressure, such as velvet or crepe, without changing the appearance of the goods, that is to say, the process of the invention does not deleteriously affect print-sensitive materials and does not alter their piles.
The process provided by the invention can be carried out in existing systems, after certain modifications, as well as in combination with any kind of heating, drying, fixing, and condensing methods.
The process of the invention may be carried out with electronic control, thus enabling smooth interoperation between discharge assembly and evaporation section.
A further advantage of the process according to the invention is the reduction in chemical consumption.
A special advantage of the method provided by the invention is the fact that, as required, the finishing and/or application of chemicals and/or dyestuffs and/or auxiliary agents can be effected either on the surface or in the core of the goods to be coated and also on the surface, as well as in the core simultaneously.
A further advantage of the process embodying the principles of the invention is the fact that the necessary setting periods are shorter than in the padding technique.
In difficult cases where various liquors with limited compatibility must be applied, the invention permits simultaneous application without the risk of a liquor breakdown.
An additional field of application is provided for a combined operation, e.g., with the naphthalating process, as a consequence of invention-induced economizing of a drying operation between impregnating and final dyeing.
Due to the constantly even coating of the product made possible by the process of the invention, maximum uniformity and, thus, optimum final quality of fabric, both in length and in width of the goods, can be attained.
With regard to the coating of dyestuffs and/or chemicals or finishing agents in partial widths, the method of the invention provides a new field of application that cannot be handled by the padding technique.
Finally, a special advantage is seen in the fact that unlike, for example, padding there are no leveling problems to contend with, even with the greatest possible working widths.
The practical application of the process according to the invention also results in better creasing angles and abrasion resistance for all types of textiles and non-woven fabrics.
In recapitulation, the following can be stated: The great advantage of the method of the invention over the familiar spray methods employing compressed air is the fact that the dyestuffs, chemicals or other finishing materials can be applied very evenly to the textiles. In addition, this method reduces considerably the cost of power consumption for drying purposes heretofore necessary for padding the material.
Furthermore, better hydrophobic effects can be attained with this process. Heretofore, certain finishing materials, such as non-water-soluble emissions, could only be applied with an emulsifier. However, this emulsifier had a disturbing effect on the appearance of the finished product, e.g. in the case of hydrophobic finishing. It is now possible to apply these materials with a lesser amount of emulsifier and without water.
Another advantage of this process lies in the treatment of goods that cannot be padded, e.g. knitted goods. For example, for better dyestuff absorption they may be sprayed with caustic soda prior to dyeing, using suitable wetting agents and, where necessary, also thickeners in order to obtain optimum distribution of the liquid in the atomizing cone. Knitted goods shrink considerably during the treatment on a padding mangle, so that the original width cannot be maintained. This can be fully avoided by the process according to the invention.
Moreover, the method according to the invention has the advantage that textiles can be dyed or treated on one side only, for example, in order to obtain certain effects or color runs, e.g. in materials known as degrade fabrics in which a color run from one side to the other is desirable.
Furthermore, finishing materials made from artificial resins can be applied through atomization to obtain the familiar crease-resistant, self-smoothing properties of the fabric and abrasion resistance. Excellent creasing angles can be obtained with small amounts of coatings of finishing agents made from artificial resins.
Advantageously, the method of the invention can also be employed for water-repellent finishing. Particularly, water-repellent finishing can be effected with small amounts of emulsifiers that counteract the water-repellent effect. Moreover, one-sided application of water-repellent finishing is possible here, so that the water-repellent effect of the material can advantageously be achieved from one side only, while the other side, e.g. the inner surface of garments, continues to "breathe".
Furthermore, finishing agents can be made with this method that give a hand (or handle) to the fabric. In certain materials a rough or smooth feel of the surface is desirable. In this case, one-sided application of the textile finishing material can achieve effects that heretofore have not been possible with the dipping technique.
Another preferred field of application of the process according to the invention consists in a uniform application of textile lubricants in the spinning mill.
Sizing along the principles of the invention reduces the cost of power consumption for drying.
In a practical embodiment of the invention, airless spray guns are employed under high pressure to carry out the process of the invention to apply dyestuffs and/or chemicals or finishing materials to the textiles being treated for the purpose of pretreating, bleaching, dyeing or finishing them. Only the minimum amount of liquid needed to disperse the dyestuff or to solve the chemicals or the other textile finishing agents need be sprayed, so that high concentrations of the dyestuffs, chemicals or other textile finishing agents are obtained.
In another practical embodiment of the invention, a plurality of such airless spray guns may be employed in a row along the width of the web of fabric.
Preferably, the liquids, chemicals or other finishing materials have a high surface tension for the formation of droplets, as well as a low viscosity (ranging from 20 to 100 cp).
A further advantage is the fact that the dyestuffs and/or chemicals or the other finishing agents can be coated in accurately measured batches.